Findings of previous observational investigations about the relation between circulating 25-hydroxyvitamin D (25(OH)D) and hypertension (HTN) in children and adolescents were inconsistent. This systematic review and dose-response meta-analysis summarized the relation between circulating 25(OH)D and childhood HTN in epidemiologic studies.

A systematic search of four electronic databases, MEDLINE (PubMed), Web of Science (ISI) and Scopus and Google Scholar was performed up to April 2025. A total of 21 observational investigations that examined the relation of circulating 25(OH)D among children and adolescents and HTN, and reported RRs or ORs with 95% CIs were included. Findings demonstrated that greater circulating 25(OH)D had an association with a 19% decline in odds of HTN (95%CI 0.70, 0.93). Although a significant inverse relation was seen among highest 25(OH)D concentrations and odds of HTN in cross-sectional studies (OR = 0.81; 95% CI 0.69, 0.96), cohorts did not illustrate a significant relation (RR = 0.76; 95% CI 0.52, 1.12). Also, the observed relation of 25(OH)D levels and odds of HTN was significant in non-Asian societies (OR = 0.66; 95% CI 0.53, 0.82), but not in Asian societies (OR = 0.99; 95% CI 0.88, 1.12). Linear dose-response analysis demonstrated that each 25 nmol/L increment in 25(OH)D concentrations was related with a 5% marginal decrease in odds of HTN (OR = 0.95; 95% CI 0.90, 1.01). Furthermore, a significant U-shape nonlinear association was found between 25(OH)D concentrations and HTN.

In conclusion, greater levels of circulating 25(OH)D levels was linked to a significantly decreased odds of childhood HTN. Moreover, the association was mostly observed in cross-sectional studies and non-Asian countries. Also, non-linear analysis has found a U-shape significant association between circulating 25(OH)D concentrations and HTN in children. The most reduction in odds of HTN was seen in optimum levels of circulating 25(OH)D levels from 35 to 75 nmol/L.

PROSPERO registration no. CRD42022380969.

This meta-analysis of epidemiologic studies disclosed an inverse association among circulating 25(OH)D levels and odds of elevated blood pressure among children and adolescents.

Obesity during pregnancy is associated with increased risk for vitamin D deficiency in both the mother and offspring. Free or unbound 25-hydroxyvitamin D (25(OH)D) is the biologically active form as compared to total 25(OH)D, which may be important in the assessment of vitamin D status during conditions like pregnancy where vitamin D binding protein (VDBP) is affected. Little is known about how pre-pregnancy BMI affects changes in vitamin D markers during pregnancy. This is a secondary analysis of data and biospecimens from the 2009-2014 National Children's Study (NCS). The current analysis included 50 participants (50 % normal weight [18.5 ≥BMI<25 kg/m2] and 50 % overweight/obese [BMI≥25 kg/m2]), recruited across four US Census regions (Northeast, South, West, and Midwest), with serum samples available from three time points during pregnancy: 1st half (<25 weeks), 2nd half (>25 weeks) and birth. Total 25(OH)D was quantified via liquid chromatography-tandem mass spectrometry (LC-MS/MS), and commercially available assays were used to measure free 25(OH)D and VDBP. Percent free 25(OH)D was calculated as free25OHDtotal25OHDx100. Linear mixed effect models, including quadratic gestational age term were employed to exam the change in vitamin D metabolites by quadratic gestational age, as well as interactions with pre-pregnancy BMI and season of birth. A positive linear trend was observed for total 25(OH)D levels across gestation (p = 0.002), while quadratic relationships were observed for both VDBP (p < 0.001) and % free 25(OH)D (p = 0.001). A significant interaction was observed between gestational age and season of birth for total 25(OH)D (p < 0.001) and free 25(OH)D (p = 0.006). Furthermore, the interactive effect of gestational age and pre-pregnancy BMI was statistically significant for both total 25(OH)D (p = 0.002) and % free 25(OH)D (p = 0.007). Our results suggest that among a sample of US women both season of birth and maternal pre-pregnancy BMI affected changes in vitamin D metabolites across pregnancy. The effects of maternal BMI on changes in total 25(OH)D and % free 25(OH)D across pregnancy suggest maternal obesity may differentially affect vitamin D metabolism in pregnancy. Future research is necessary to compare differences in vitamin D metabolism among obesity affected pregnancies as compared to healthy-weight counterparts.

Many adults become vitamin D deficient or insufficient during winter at northerly latitudes when cutaneous vitamin D synthesis does not occur. Vitamin D accumulates in adipose tissue and people with overweight or obesity are more likely to have low systemic vitamin D. This randomized controlled trial demonstrates that regular exercise completely maintains serum concentrations of the active vitamin D metabolite 1,25(OH)2D3 over winter and may ameliorate the decline in 25(OH)D status in overweight men and women, even without weight loss. The binding of 1,25(OH)2D3 to the vitamin D receptor mediates the crucial role for vitamin D in the healthy function of multiple organ systems and vitamin D supplementation does not impact circulating 1,25(OH)2D3. Thus, the VitaDEx study provides causal evidence that exercise plays an important role in vitamin D metabolism that is distinct from the effects of oral supplementation.

Vitamin D is a sterol prohormone with no intrinsic biological activity. Calcitriol, the active form of vitamin D, is synthesized in the kidneys. It has well-known pleiotropic and cytoprotective properties. In addition to regulating parathyroid hormone secretion and enhancing gut calcium absorption, it exhibits antioxidant, anti-inflammatory, antiproliferative, and antineoplastic effects. However, the role of vitamin D in AKI is unclear, unlike in CKD. Thus, this review aimed to understand how dysregulated vitamin D homeostasis occurs in AKI, as well as to explore how vitamin D deficiency and excess influence AKI. A comprehensive literature search was conducted between January 2000 and June 2024 to uncover relevant works detailing vitamin D homeostasis in health as well as investigating the impact of vitamin D deficiency and excess in humans, animals, and in vitro cell models of AKI. According to the findings of this review, vitamin D appears to have a reciprocal relationship with AKI. Acute renal injury, among other factors, can cause hypo- or hypervitaminosis D. Conversely, AKI can also be caused by vitamin D deficiency and toxicity. Even though hypovitaminosis D is associated with AKI, it is uncertain how it impacts AKI outcomes in distinct clinical scenarios. Newer therapeutic options might emerge as a result of understanding these challenges. Vitamin D supplementation may ameliorate renal injury but needs further validation. Furthermore, hypervitaminosis D has also been implicated in AKI by causing hypercalcemia and hyperphosphatemia. It is crucial to avoid prolonged, uncontrolled, and unsupervised supraphysiological vitamin D administration, especially intramuscular injection.

To establish accurate population-based reference intervals (RIs) for serum 25-hydroxyvitamin D [25(OH)D] using the refineR indirect method and real-world data (RWD), accounting for demographic, methodological, and seasonal factors.

A retrospective analysis of 130,030 serum 25(OH)D samples collected from 2018 to 2022 at a tertiary hospital in Barcelona was performed. Samples were measured using VDSP-certified Liaison and Atellica immunoassays. The refineR algorithm was employed to establish RIs, utilizing Box-Cox transformations to adjust for data distribution. Demographic variables (sex and age), assay differences, medical department and seasonal variations were analysed. RIs were verified using a subset of healthy individuals.

The median serum 25(OH)D level was 25 ng/mL (62.5 nmol/L). Vitamin D deficiency (≤20 ng/mL, ≤50 nmol/L) was observed in 34.2% of samples, and severe deficiency (≤12 ng/mL, ≤30 nmol/L) in 12.6%. The default Box-Cox transformation estimated RIs of 11.5-64.5 ng/mL (28.7-161.2 nmol/L), while the modified Box-Cox transformation yielded RIs of 14.2-65.9 ng/mL (35.5-164.7 nmol/L). Women exhibited wider RIs (14.5-68.6 ng/mL, 36.2-171.5 nmol/L) compared to men (11.6-57.3 ng/mL, 29-143.2 nmol/L). Method-specific RIs were 10.2-58.6 ng/mL (25.5-146.5 nmol/L) for the Liaison assay and 9.9-59.3 ng/mL (24.7-133.2 nmol/L) for the Atellica assay. The lowest RIs were observed in outpatients (4.3-46.4 ng/mL, 10.7-116 nmol/L) and endocrinology patients (5.5-43.9 ng/mL, 13.7-109.7 nmol/L). Seasonal variation significantly impacted RIs, with higher levels during summer months.

The refineR algorithm effectively established population-based RIs for serum 25(OH)D in Barcelona, revealing significant demographic and seasonal variations. Redefining 25-hydroxyvitamin D thresholds based on population-specific data may reduce unnecessary screening and supplementation, minimizing associated risks. This study highlights the need for population-, seasonal-, and method-specific RIs to improve vitamin D assessment and management.

(1) Background: In recent years, there has been a growing interest in understanding the innate immunity of the mouth, particularly the mechanisms through which vitamin D influences oral health. Researchers have increasingly focused on the association between vitamin D and the antimicrobial peptide LL-37 since the CAMP gene, responsible for encoding the LL-37 peptide, is a direct target of both vitamin D and its receptor (vitamin D receptor, VDR). This study aimed to explore the correlation between the 25-hydroxyvitamin D (25(OH)D) levels and the concentration of the LL-37 peptide in both serum and saliva. The objective was to compare the serum concentrations of 25(OH)D and ll-37 with those in saliva and to access the correlations between the two compounds. (2) Methods: Serum and whole saliva samples were collected from 72 healthy adults (mean age 28.68 ± 8.35). The levels of 25(OH)D and LL-37 were assessed in both the saliva and serum samples using commercially available enzyme-linked immunosorbent assay (ELISA) kits. (3) Results: The 25(OH)D levels in the serum (median 5.92 ng/mL, min-max 2.7-10.4 ng/mL) correlated with the LL-37 serum levels (62 ng/mL, min-max 18-378 ng/mL; Pearson's r 0.328, p = 0.005). Additionally, the 25(OH)D levels in saliva (median 1.16 ng/mL, min-max 0.54-2.12 ng/mL) strongly correlated with the LL-37 salivary levels (median 44 ng/mL, min-max 6.5-205 ng/mL; Pearson's r 0.667, p < 0.001). The 25(OH)D salivary levels demonstrated a robust correlation with the LL-37 salivary levels. (4) Conclusions: This discovery emphasizes the complex interplay between vitamin D and LL-37 and lay the groundwork for the further exploration of vitamin D's role in oral immune function.

Multiple sclerosis (MS) onset is caused by genetic and environmental factors. Vitamin D has been identified as contributing environmental risk factor, with higher prevalence at latitudes further from the equator. Mongolia, at 45°N, has limited sunlight exposure, increasing the population's risk for vitamin D deficiency.

To compare vitamin D levels between persons with MS (pwMS) and persons without MS and to identify factors associated with low vitamin D.

We investigated associations with vitamin D levels using data from MS cases and controls from Mongolia. We used linear mixed-effects regression with fixed effects (case status, sociodemographics, and predefined variables) and participant-specific random intercepts.

Of 62 participants (31 pwMS, 31 controls), pwMS had lower summer [median 23.00 ng/ml (interquartile range 11.30-31.50) vs. 25.00 ng/ml (19.25-32.00)] and winter vitamin D levels [21.00 ng/ml (10.60-27.60) vs. 23.50 ng/ml (15.55-28.60)], with a smaller seasonal decline. Vitamin D deficiency was more prevalent in pwMS. None of these findings reached statistical significance. Winter season and being breastfed as a child were associated with significantly lower vitamin D levels.

Vitamin D deficiency was common among pwMS, which could be influenced by behavioural factors. These findings may inform more targeted recommendations for pwMS to maintain sufficient vitamin D levels.

Sunlight exposure plays an important role in human health, impacting processes such as mood, blood pressure regulation, and vitamin D3 production. Solar ultraviolet B radiation initiates vitamin D3 synthesis in the skin, which is subsequently metabolized into its biologically active form. UVB exposure plays a key role in enabling vitamin D3 synthesis, but it can also contribute to skin carcinogenesis, creating a complex interplay between its beneficial and harmful effects. Vitamin D deficiency, affecting over half the global population, is linked to a range of chronic diseases, including cancers, cardiovascular conditions, and autoimmune disorders. Simultaneously, excessive solar UVB exposure increases the risk of non-melanoma and melanoma skin cancers through mechanisms involving DNA damage and oxidative stress. This review examines the dual role of UVB radiation in health and disease, focusing on the mechanisms of cutaneous vitamin D3 synthesis, the epidemiology of skin cancer, and the protective roles of vitamin D3's photoproducts and its active metabolite, 1,25-dihydroxyvitamin D3. Understanding these interconnections is critical for developing strategies that balance adequate sun-induced vitamin D3 production with skin cancer prevention.

Background: Vitamin D and iron deficiencies are prevalent among Moroccan women of reproductive age (WRA). Research suggests that Vitamin D deficiency (VDD) may impair iron bioavailability, potentially leading to iron deficiency (ID) and anemia. Objectives: This study investigates associations between vitamin D status, iron levels, and anemia risk in WRA, aged 18-49, from Meknes, Morocco. Methods: A cross-sectional study was conducted among 463 participants, measuring serum 25(OH)D, blood count parameters, iron, ferritin, C-reactive protein, and creatinine. Lifestyle factors, including dietary intake, sun exposure, and physical activity, were assessed through validated questionnaires, and anthropometric data were collected. Linear and logistic regression models analyzed associations, while ROC analysis evaluated VDD's predictive accuracy for ID and anemia. Results: VDD (25(OH)D < 20 ng/mL) was significantly associated with reduced hemoglobin, hematocrit, red blood cells, and ferritin (all p < 0.01), indicating vitamin D's role in erythropoiesis and iron storage. Multivariate logistic regression showed that VDD increased the risk of anemia (OR: 7.17, 95% CI: 3.19-19.28, p < 0.001), ID (OR: 2.20, 95% CI: 1.32-3.77, p = 0.007), and IDA (OR: 4.10, 95% CI: 1.73-12.08, p = 0.004). Dietary iron intake was inadequate, showing minimal protective effects against anemia and ID (β(SE): -0.08(0.03), p = 0.030 and β(SE): -0.05(0.02), p = 0.037). Conclusions: VDD is a significant risk factor for impaired iron status and anemia in Moroccan WRA, highlighting the need for targeted nutritional interventions and further research.

Background: The condition of vitamin D (25OHD) deficiency represents an important public health problem. In Europe, hypovitaminosis is common not only in the elderly population but also between 50 and 70 years, both in males and females. Data regarding vitamin D intake in the Italian population are very limited. In a recent paper, reporting data collected by a specific Frequency Food Questionnaire (FFQ), we observed in a small group of healthy subjects that the dietary consumption of vitamin D, both in females and males, was far below the average. Methods: With the aim of expanding our preliminary data, we conducted a survey on a large cohort of subjects from different areas of Northern, Central, and Southern Italy. The FFQ contained 11 different questions regarding the amount and type of intake of foods containing ergocalciferol and cholecalciferol. It was submitted to 870 subjects, 627 females and 243 males, with an age range from 40 to 80 years; 31.6% of the studied population was apparently in good health, while 68.4% were affected by different pathologies. Results: The present data confirm previous observations: the global quantity of vitamin D intake in 14 days was 70.8 μg (±1.8 SE, ±54.4 SD) in females and 87.5 μg (±1.9 SE, ±57.1 SD) in males; the mean daily intake of vitamin D in females and males was 5.05 μg (±0.5 SE, ±3.8 SD) and 6.25 μg (±0.21 SE, ±4.1 SD), respectively. In healthy subjects, a gradual decrease was observed in the overall intake of vitamin D in both females and males according to an increase in age bracket, ranging from 74.5 μg and 103.8 μg in the 40-50 age group to 54.5 μg and 87.8 μg in the 71-80 age group, respectively. Conclusions: In conclusion, the present data, collected in a large Italian cohort, underscore that the daily intake of vitamin D is far below the recommended daily average, thereby contributing to the development of potential hypovitaminosis.

To use the prevalence of prenatal/infancy interglobular dentine (IGD) as a proxy for suboptimal vitamin D status and explore its link to mortality, biological sex, cultural behaviours and environmental factors during the end of the pre-industrial/ beginning of the industrial period.

50 skeletons from the St. Antoine cemetery (1799-1854), Montreal, Quebec with a well-preserved first mandibular molar.

Thin sections were prepared for histological examination of IGD in crown dentine.

IGD prevalence was 74 % (37/50) and not significantly correlated statistically to sex and age-at-death. Most IGD occurred at birth and up to 3 years-old, six individuals were affected in utero, 54 % of the sample (27/50) presented longstanding IGD and six individuals displayed multiple IGD episodes.

Prenatal IGD episodes revealed suboptimal maternal vitamin D levels, which, alongside a high frequency of IGD episodes around birth/from birth until a certain age, suggest cultural influences. Multiple and longstanding IGD episodes might also reflect suboptimal seasonal vitamin D attainment.

This study provides in-depth data on IGD within a relatively large archaeological North American sample, proving relevant to epidemiological studies on suboptimal vitamin status in 19th century Montreal.

The total number of IGD episodes is underestimated due to methodological biases; first-generation migrants in this study could not be identified and excluded from the sample.

Use of a larger sample with a wider age-at-death range; further research on infants and children to investigate links between growth and lesion formation and visibility.

Habitual dietary changes that could help reduce the potential consequences of excessive body mass, such as hyperlipidemia and increased cardiovascular disease risk, are needed. The aim of this study is to assess the impact of a farmed-salmon-based dietary intervention on lipid profile parameters in young women with excessive body mass.

The 8-week intervention involved 38 pair-matched women aged 18-30 years with excessive body weight defined as BMI ≥ 25.0 kg/m2. Participants were randomly assigned to the intervention (200 g of smoked salmon weekly) or the control group. Lipid profile parameters (total cholesterol (TC), high-density lipoprotein (HDL), low-density lipoprotein (LDL), triglycerides (TAG)), as well as atherogenic indices (Atherogenic Index of Plasma (AIP), Atherogenic Coefficient (AC), Cholesterol Index (Cholindex), Castelli Risk Index 1 (CRI-1), Castelli Risk Index 2 (CRI-2) and the TAG/HDL ratio) were assessed before, during, and after the intervention.

At baseline, 47% of participants had at least one of the lipid profile parameters outside the recommended range. No statistically significant differences were observed in the TC, HDL, non-HDL, LDL, or TAG concentrations or in the various atherogenic indices between the intervention and the control group after the 8-week-long intervention. However, differences in the change of the LDL concentration were noted, with a decrease of 8.2 ± 20.7 mg/dL in the intervention group compared to an increase of 9.5 ± 20.0 mg/dL in the control group (p = 0.011), as well as in the change of the Cholindex for which a median decrease of 4.4 mg/dL was noted in the intervention group, while a median increase of 0.8 mg/dL in the control group was observed (p = 0.040). Additionally, across participants with a waist-to-height ratio (WHtR) greater than 0.5, an increase of 50.0 ± 68.3 mg/dL in the intervention group and a decrease of 8.6 ± 56.6 mg/dL in the control group was noted for the TAG concentration change (p = 0.040).

Concerning the observed beneficial influence of increasing farmed salmon intake to the recommended fish-intake amounts on decreasing LDL and Cholindex in young women with excessive body weight after 8 weeks, it seems that such a diet alteration might be recommended for this group to decrease their risk of cardiovascular disease in the future. Nonetheless, regarding the diverse influence on TAG, further studies are needed to assess the influence of increasing the intake of fatty fish available on the market at present on human health.

Young women are often at risk of vitamin D deficiency, while fatty fish can provide significant amounts of it, which is especially important when no vitamin D skin synthesis is possible due to limited sunshine exposure. This study aimed to analyze the impact of increasing the intake of salmon in various forms (smoked salmon, salmon sausages) on vitamin D status of young women in autumn.

The 8-week intervention involved 120 non-obese women, aged 20-25 years. Participants were randomly assigned to one of three groups: smoked salmon (25 g/day), salmon sausage (100 g/day), or a control group. Both intervention products provided approximately 5 µg of vitamin D daily. Serum concentrations of 25(OH)D as well as vitamin D intakes were assessed pre-, mid-, and post-intervention.

The median vitamin D intake at baseline was 2.7-3.4 µg/day and did not differ between the groups (p > 0.05), while during the intervention, it was highest in the smoked salmon group (p < 0.001) and amounted to 7.3 µg/day. While all groups experienced a decrease in 25(OH)D serum concentrations, the decrease was significantly smaller in the salmon sausage group compared to the control group (-4.3 vs. -15.0 nmol/L, p < 0.05), and no significant difference was observed between the smoked salmon and control group after 8 weeks (p > 0.05). Moreover, in the salmon sausage group, the intervention was more effective among participants with an inadequate vitamin D status at baseline (25(OH)D change after the intervention: -3.0 vs. -5.4 nmol/L, p < 0.05; inadequate vs. adequate baseline vitamin D status).

Increasing the intake of salmon, and hence of vitamin D, was not enough to maintain the vitamin D status of young women in autumn. It seems that other, not-yet-fully-understood factors, may influence vitamin D absorption and/or metabolism, thereby affecting the outcomes of such interventions indicating that further research is needed. Nevertheless, it may be concluded that increasing salmon sausage intake might aid slow down the natural decline of 25(OH)D in young women in autumn.

Background: The most recent vitamin D data from the National Health and Nutrition Examination Survey (NHANES) have not been examined. We used data from NHANES to describe trends in 25-hydroxyvitamin D [25(OH)D] from 2011 to 2018 and for the most recent cycle (2017-2018) to identify groups with lower levels of 25(OH)D and factors predictive of 25(OH)D. Methods: The 31,628 participants were weighted to represent the entire U.S. population. For each 2-year NHANES survey cycle (2011 to 2018), we calculated the weighted median (25th and 75th percentiles) of 25(OH)D and the proportion of the population within the following categories (nmol/L): <30, 30-<50, 50-<75, 75-<125, and ≥125. For 2017-2018, we stratified by demographic and behavioral factors. Multivariate linear regression identified variables predictive of 25(OH)D. Results: The median 25(OH)D (nmol/L) increased slightly from 2013-2014 [66.5 (25th and 75th percentiles: 51.3, 83.0)] to 2017-2018 [68.7 (52.3, 87.8)], and the prevalence of 25(OH)D <50 nmol/L decreased slightly (23.4% vs. 21.3%). In 2017-2018, characteristics associated with lower 25(OH)D were age (12-39 years), male gender, non-Hispanic Black, higher BMI, lower income and education, winter season, not taking vitamin D supplements, or "never" using sunscreen. When stratified by age, race/ethnicity, and gender simultaneously, median 25(OH)D was lowest among non-Hispanic Black females aged 12-19 (38.5 nmol/L) or 20-39 (38.9 nmol/L). Predictors of 25(OH)D level differed by race/ethnicity, e.g., increasing BMI was associated with larger decrements in 25(OH)D among Mexican Americans. Conclusions: This analysis is the first to examine vitamin D levels stratified by multiple characteristics simultaneously. This strategy identified populations at higher risk for health sequelae due to low levels of vitamin D. For example, high levels of deficiency were found in non-Hispanic Black females of reproductive age.

Objective: The aim of our study was to compare the total 25(OH)D fraction, the bioavailable vitamin fraction, and the free vitamin D fraction in spring and fall in a group of healthy individuals. Methods: In our study, we collected blood samples from healthy participants at the end of both summer and winter, and measured serum levels of albumin, DBP, and 25(OH)D. Utilizing these data, we calculated the percentage of free and bioavailable vitamin D. Our cohort comprised 87 participants, with a male-to-female ratio of 14:73, aged 35.95 ± 12.55 years, ranging from 19 to 70 years. We employed the chemiluminescence method to determine the vitamin 25(OH)D levels, the ELISA method was utilized to determine DBP levels, the albumin BCP Assay was performed using the ADVIA biochemical analyzer (Siemens) and an online calculator was used to determine the free and bioavailable 25(OH)D levels. Results: Our findings indicate significantly lower 25(OH)D levels in winter (44.13 ± 17.82 nmol/L) compared to summer (74.97 ± 22.75 nmol/L; p < 0.001). For vitamin D binding protein there was no significant difference from summer (236.2 ± 164.39 mg/L) to winter (239.86 ± 141.9 mg/L; p = 0.77), albumin levels were significantly higher in summer (49.37 ± 4.15 g/L vs. 47.97 ± 3.91 g/L, p = 0.01), but the magnitude of the change may not be large enough to be solely responsible for the stability of vitamin D levels throughout the year. In the winter season a significantly lower calculated bioavailable 25(OH)D vitamin (7.45 ± 5.66 nmol/L against 13.11 ± 8.27 nmol/L; p < 0.001) was observed, and the free fraction also showed a significant decrease (17.3 ± 12.9 pmol/L versus 29.7 ± 19.1 pmol/L; p < 0.0001). We observed a moderately positive correlation between 25(OH)D and bioavailable percentage in winter (r = 0.680; p < 0.001), in contrast with a lower positive association in summer (r = 0.343; p < 0.001). Conclusion: Our data suggest a positive correlation between total and bioavailable 25(OH)D levels. In addition to the statistically significant variation in 25(OH)D between the two observation periods, there was an additional variation in the free vitamin D percentage. The summertime synthesis of vitamin D in the skin could contribute directly to the free fraction of vitamin D. Standardizing the measurement of free 25(OH)D and clinical studies is necessary to establish reference values before these methods can be implemented in clinical practice.

Vitamin D3 is essential for several functions in the human body and the demand is usually covered by natural reactions in skin with UV radiation delivered by the sun. But living beyond a latitude of 35° can lead to a lack of sufficient exposition to the deciding wavelength. Here, many countries fortify their milk prophylactically with artificial vitamin D3. However, the precursor molecule of vitamin D3 (7-deydrocholesterol) is already naturally located in the milk fat globule membrane. Thus, this study deals with the transformation of the naturally occurring 7-dehydrocholesterol into vitamin D3 through UV treatment of the milk - a mechanism that was observed a century ago only indirectly. Different parameters such as temperature (10 - 50°C), fluid flow regimen (turbulent vs. laminar thin film, i.e., 0.6 mm) and wavelength (254, 280 and 313 nm) were investigated in this study for their efficiencies. The UV dose of each experiment was measured with chemical actinometry delivering the actually applied dose reaching the milk. Thus, the connection between applied UV dose and generated vitamin D3 content in the milk measured quantitively with LC-MS/MS was evaluated here that both were not possible a hundred years ago. The experimental results revealed that temperature generally promotes the vitamin D3 formation at 254 nm. Further, a turbulent flow is not as efficiently treated as a laminar thin film flow that is as narrow as 0.6 mm. As expected from absorbance spectra of the precursor molecule 7-dehydrocholesterol, 280 nm turned out to be the most efficient wavelength, followed by intermediate success through irradiation with 254 nm and almost no effect by 313 nm. Generally, it was shown that vitamin D3 concentration of milk was easily increased by UV treatment with today's technologies and that adjustment of certain physical parameters have a significant effect on the efficiency.

A paucity of vitamin D is a common deficiency globally, with implications for many aspects of health besides the well-known impact on musculoskeletal health. The two sources of vitamin D are through oral intake, or through endogenous synthesis in the skin when exposed to ultraviolet radiation in sunlight. Assessing nutritional needs, whether by food, food fortification or supplementation, is aided by an understanding of local potential for cutaneous synthesis of the vitamin, dependent on latitude and climate, personal skin type and local culture. To aid these discussions we provide indicative exposure times for the maintenance of vitamin D status as a function of latitude, month and skin type, for the clear-sky case and all-sky conditions, for an ambulatory person wearing modest skirt/shorts and T-shirt. At latitudes greater than ±40 degrees, lack of available sunlight limits vitamin D synthesis in some months for all, while at the equator exposure times range from 3 to 15 min at noontime, for white and black skin, respectively. Rather than a sun exposure prescription, the data are intended to show where nutritional vitamin D intake is necessary, advisable, or can be mitigated by sun exposure, and allows for such advice to be personalized to account for different sub-groups in a multicultural population.

In Canada, nutrition policy, as outlined in the Nutrition for Healthy Term Infants recommendations, includes a daily vitamin D supplement of 10 μg (400 IU) for breastfed infants and young children to support adequate vitamin D status.

This study aimed to report on adherence to vitamin D supplementation recommendations for breastfed infants (≤12 months); and for children breastfed >12 mo.

Canadian Community Health Survey (paired-cycles 2015/2016 and 2017/2018) maternal experiences data for infants born 2012-2018 who received any breastmilk formed the sample (n = 7079). Whether the infant was given a vitamin D supplement (yes/no) and the frequency (daily/almost every day, 1-2/wk, or <1/wk) were surveyed. Weighted data (95% CI) were summarized according to breastfeeding history (exclusive to 6 mo and continuing; partial to 6 mo and continuing; and stopped ≤6 mo). Correlates of supplement adherence were explored using logistic regression.

Overall, 87.1% (95% CI: 85.9%, 88.3%) of participants reported giving their infant (≤12 mo) a vitamin D supplement, and of these, 83.3% (95% CI: 81.9%, 84.7%) did so daily/almost every day, 12.4% (95% CI: 11.1%, 13.7%) did so 1-2/wk, and 4.3% (95% CI: 3.6%, 5.0%) did so <1/wk. Lower adjusted odds of adherence were observed among participants reporting: stopped breastfeeding ≤6 mo, lower education or income, recent immigration, and overweight prepregnancy body mass index; higher odds of adherence were observed in the western provinces. Regarding mothers of children >12 mo and breastfed (n = 2312), 58.0% (95% CI: 54.9%, 61.1%) gave a vitamin D supplement daily/almost every day.

Adherence to providing a vitamin D supplement to breastfed infants is high in Canada. Nonetheless, we estimate that ∼27% of mothers are nonadherent to daily/almost every day administration of a vitamin D supplement and that adherence declines in children breastfed >12 mo. Further promotion to support uptake of the current guidance may be necessary, particularly for parents of recent immigration or lower socioeconomic status.

This comprehensive review explores the multifaceted role of vitamin D (VD) in critically ill children, examining its implications for clinical outcomes. Although this substance has long been known for its function in maintaining bone health, it is now becoming more widely known for its extensive physiological effects, which include immune system and inflammation regulation. Observational research consistently associates VD levels with outcomes like duration of hospitalization, mortality, and illness severity in critically ill pediatric patients. Mechanistically, it exerts anti-inflammatory and endothelial protective effects while modulating the renin-angiotensin system. Increasing VD levels through supplementation presents promise as a therapeutic strategy; however, further research is necessary to elucidate optimal dosage regimens and safety profiles. This review emphasizes the significance of comprehending the intricate relationship between VD and critical illnesses among pediatric populations.

In terms of vitamin D food fortification, there are a number of important considerations in relation to selection of the food vehicle and fortificant. While there has been much research focus on the ability of fortified foods to improve vitamin D status, other considerations, such as sensory properties and acceptability, cost, and public attitudes around vitamin D-fortified foods, have received less attention. Thus, the present narrative review aimed to summarize the existing knowledge around these important considerations. In summary, its findings suggest that: i) vitamin D addition to various food vehicles, at levels consistent with the supply of part or all the recommended intake, does not alter their sensory characteristics or overall acceptability; ii) overall, vitamin D fortification of foods is relatively cost-effective, despite the fact that some attitudinal studies highlighted participant concerns about the potential cost/expense of vitamin D-fortified foods; iii) evidence from various attitudinal studies suggest a high level of acceptance and/or purchase intention (i.e., extent to which customers are willing and inclined to buy) of vitamin D-fortified food products by the general public; and iv) there have been repeated calls for vitamin D public health educational/information campaigns to help educate consumers about the health risks associated with vitamin D deficiency and nutritional benefits associated with consumption of vitamin D-fortified foods. Such campaigns could positively mediate attitudes and acceptance of vitamin D-fortified foods amongst the public, and could also help address misconceptions and allay fears around vitamin D for concerned individuals. Lastly, the findings of the present review also highlight the existence of between-country differences, even within Europe, in relation to attitudes and purchase intention of vitamin D-fortified foods and the perceived appropriateness of certain food vehicles for vitamin D fortification, as well as the best mix of communication channels for a vitamin D public health educational/information campaign.

Vitamin D3 synthesis in human skin is initiated by solar ultraviolet radiation (UVR) exposure of precursor 7-dehydrocholesterol (7DHC), but influence of age on the early stage of vitamin D3 metabolism is uncertain. We performed a prospective standardised study in healthy ambulant adults aged ≥65 and ≤40 years examining (1) if baseline skin 7DHC concentration differs between younger and older adults and (2) the impact of older age on serum vitamin D3 response to solar simulated UVR. Eleven younger (18-40 years) and 10 older (65-89 years) adults, phototype I-III, received low-dose UVR (95% UVA, 5% UVB, 1.3 SED) to ~35% of the body surface area. Biopsies were taken for 7DHC assay from unexposed skin, skin immediately and 24 h post-UVR, and blood sampled at baseline, 24 h and 7 d post-UVR for vitamin D3 assay. Samples were analysed by HPLC-MS/MS. Baseline skin 7DHC (mean ± SD) was 0.22 ± 0.07 and 0.25 ± 0.08 µg/mg in younger versus older adults (no significant difference). Baseline serum vitamin D3 concentration was 1.5 ± 1.5 and 1.5 ± 1.7 nmol/L in younger versus older adults, respectively, and showed a significant increase in both groups post-UVR (no significant differences between age groups). Thus, skin 7DHC concentration was not a limiting factor for vitamin D3 production in older relative to younger adults. This information assists public health guidance on sun exposure/vitamin D nutrition, with particular relevance to the growing populations of healthy ambulant adults ≥65 years.

Vitamin D, as a steroid hormone, has multiple effects on human body and its deficiency has been associated with an increased risk of heart failure (HF) and unfavorable outcomes. The present study investigated the prevalence of vitamin D deficiency (VDD) and its relationship with cardiometabolic parameters in patients hospitalized for HF living in the city of Recife (latitude 8° South).

Analytical cross-sectional study, with men and women aged 40-64 years. The HF group was recruited during hospitalization due to decompensation. A matched control group was recruited from the general endocrine clinics. Vitamin D status was assessed by measuring serum 25-hydroxyvitamin D (25OHD), considering deficiency when 25OHD <20 ng/mL (<50 nmol/L).

A total of 243 patients were evaluated (HF group: 161, control group: 82). Lower serum 25OHD levels were observed in the HF group (25.2±9.4 vs. 30.0±7.7ng/mL; p<0.001), as well as a higher prevalence of VDD (27.3% vs. 9.8%; prevalence ratio, 2.80; 95% confidence interval, 1.38-5.67; p=0.002). In patients with HF, VDD was associated with diabetes mellitus (65.9% vs. 41.0%; p=0.005) and female sex (65.9% vs. 44.4%; p=0.015). In the subgroup with VDD, higher values of hemoglobin A1c (7.9% [6.0-8.9] vs. 6.2% [5.7-7.9]; p=0.006) and dyslipidemia were also observed.

We found higher rates of VDD in patients hospitalized for HF and this was associated with deleterious laboratory metabolic parameters.

To describe the secular trend and seasonality of the incidence of hip fracture (HF) and its relationship with climatic variables during the period 2010-2019 in Catalonia in people aged ≥ 65 years. The results were analyzed by sex, age groups (65-74, 75-84, and ≥ 85), and types of fracture (extracapsular and intracapsular). Data on sex, age, type of fracture, year, and month of hospitalization of patients admitted with a diagnosis of HF between January 1, 2010 and December 31, 2019 were collected. Crude and standardized HF incidence (HFi) rates were obtained. Data on the monthly mean of climatological variables (temperature, insolation, icy days, rain, relative humidity, atmospheric pressure, and wind force) were obtained from the network of meteorological stations in Catalonia. Time series analytical statistics were used to identify trends and seasonality. Linear regression and a seasonal autoregressive integrated moving average (ARIMA) were used to analyze the relationship of each climatic parameter with fracture rates. In addition, generalized additive models were used to ascertain the best predictive model. The total number of HF episodes was 90,149 (74.1% in women and 25.9% in men). The total number of HFs increased by 6.4% between 2010 and 2019. The median age (SD) was 84.5 (7.14) and 54% of patients were ≥ 85 years of age. Extracapsular fractures were the most common (55%). The standardized incidence rates decreased from 728.1/100,000 (95% CI 738.6-769.3) to 624.5/100,000 (95% CI 648.7-677.0), which represents a decrease of 14.2% (p < 0.05). The decline was greater at older ages. There were seasonal variations, with higher incidences in autumn (27.2%) and winter (25.7%) and lower rates in summer (23.5%) and spring (23.6%). Seasonality was more pronounced in elderly people and men. In the bivariate regression analysis, high temperatures and greater insolation were negatively associated with the HF rate, while the number of icy days, rainy days, and high relative humidity were associated with a higher incidence of fractures in all age groups and sexes. In the regression analysis using the seasonal ARIMA model, only insolation had a consistently significant association with overall HFi, after adjusting by trend and other climatic parameters. While the global number of HFs grew in Catalonia due to increases in the elderly population, the standardized HF rate decreased during the years 2010-2019. There was a seasonal trend, with predominance in the cold months and correlations with climatic parameters, especially with insolation.

There has been growing interest in the potential of vitamin D food fortification in Europe as a means of addressing low vitamin D status. The WHO-FAO suggest that choosing a suitable food vehicle and ensuring the combination of the food vehicle and the fortificant will be efficacious and effective are of key importance to a successful food fortification programme. Our key objective was to conduct a systematic review and meta-analysis to investigate the effect of various animal- and plant-based food vehicles fortified with vitamin D (as D3 or D2) on circulating 25-hydroxyvitamin D [25(OH)D] concentrations. A list of prioritised food vehicles was established and we searched PubMed, Embase, Scopus and Web of Science for randomised controlled trials (RCTs) which used these vehicles individually, and which met prespecified criteria. The searches identified 49 papers which described suitable RCTs using vitamin D-fortified bread/savoury biscuits (n = 5), orange juice (n = 5), UV-mushrooms (n = 8), cheese (n = 3), yogurt (n = 5), fluid milk (n = 13), powdered milk (n = 5), eggs (n = 2), edible oils (n = 4), or breakfast cereal (n = 1). No suitable RCTs were identified for rice, maize flour, butter, margarine or dairy spreads, plant-based milk or yogurt alternatives. Random-effects meta-analyses of each food vehicle individually indicated weighted mean differences (WMD) in 25(OH)D in the range ∼9-35 nmol/L (3-15 RCT arms, depending on vehicle), and all statistically significant (P < 0.01-0.0001), with the exception of UV-mushrooms (P = 0.06). Heterogeneity was variable (I2 =33-99%, depending on vehicle), but subgroup analysis based on vitamer and dose reduced it in some instances. Sub-group analysis on the basis of whether the food vehicles were from plant-based or animal-based origin showed no significant difference in WMD (15.2 versus 15.9 nmol/L, respectively; P = 0.48). These results support the use of various animal- and plant-based food vehicles for vitamin D fortification to improve circulating 25(OH)D concentrations in populations. This work was registered with PROSPERO as CRD42023439883.

Primary antiphospholipid syndrome (PAPS) is a systemic autoimmune disorder, characterised by consistently high levels of antiphospholipid antibodies, thrombosis, and/or pregnancy morbidity. Due to various suspected causes, deficient or insufficient levels of vitamin D in the serum have been reported in patients with PAPS; however, the reports have been sporadic and inconclusive. This systematic review and meta-analysis aimed to comprehensively evaluate the serum vitamin D levels in patients with PAPS compared to controls. A protocol was registered in PROSPERO (Registration No. CRD42019132128) and a systematic literature search was conducted through Google Scholar, PubMed, Web of Science, Scopus, and ScienceDirect databases without restricting language and year. Pooled prevalence, mean difference (MD), and odds ratio (OR) along with 95% confidence intervals (CI) were determined by using a random effects model. Study quality was assessed by the Joana Brigg's Institute (JBI) protocol and publication bias was evaluated by a trim and fill funnel plot, Begg's, and Egger's tests. The pooled prevalence of vitamin D deficiency and insufficiency was found to be 32.2% [95% CI: 16.3-48.2] and 61.5% [95% CI: 40.2-82.8], respectively. Serum levels of vitamin D were considerably lower in the PAPS patients compared to controls (MD: -5.75, 95% CI: -9.73 to -1.77; p = 0.005). Multiple sensitivity analyses showed that the results remained statistically significant, demonstrating the robustness of this meta-analysis. No significant publication bias was detected in determining the MD of serum vitamin D levels in PAPS and controls. In conclusion, PAPS patients had greater rates of vitamin D deficiency or insufficiency, higher frequency of thrombosis, and lower serum vitamin D levels than healthy individuals.

Viruses can cause many human diseases. Three types of human diseases caused by viruses are discussed in this chapter: infectious diseases, autoimmune diseases, and cancers. The infectious diseases included in this chapter include three respiratory tract diseases: influenza, COVID-19, and respiratory syncytial virus. In addition, the mosquito-borne dengue virus diseases are discussed. Vitamin D can reduce risk, severity, and mortality of the respiratory tract diseases and possibly for dengue virus. Many autoimmune diseases are initiated by the body's reaction to a viral infection. The protective role of vitamin D in Epstein-Barr virus-related diseases such as multiple sclerosis is discussed. There are a few cancers linked to viral infections. Such cancers include cervical cancer, head and neck cancers, Hodgkin's and non-Hodgkin's lymphoma, and liver cancer. Vitamin D plays an important role in reducing risk of cancer incidence and mortality, although not as strongly for viral-linked cancers as for other types of cancer.

Vitamin D deficiency in relation to bone metabolism and healing has been controversial and not well studied. However, hypovitaminosis has been widely identified within the orthopedic patient population. The current best evidence suggests a lack of data on this important topic. The ability to assess patients for optimum bone healing and metabolism is still in question due to lack of a suitable reliable biomarker and multiple other unknown variables affecting bone metabolism. To compound this effect, popular dermatological precautions in the last 20 to 30 years of avoiding sunlight also have the effect of further reducing serum vitamin D production in the skin. As a proof of concept, we performed a preliminary comparative observational retrospective review of orthopedic patients undergoing fracture and arthrodesis osseous healing to determine how serum vitamin D levels are associated with bone healing along with their confounding comorbidities. Based on our review, the current accepted vitamin D levels (≥20 ng/mL) are low and insufficient for fractures and for arthrodesis osseous healing due to observed high rates (>35%) of delayed unions, and an increased (>90%) in the number of multiple confounding comorbidities affecting bone healing process that are often not mentioned or captured in this type of study in previous literature. Obesity and diabetes are significant contributory risks factors, and the preliminary findings suggest that the current accepted adequate levels may not be enough for osseous healing. These low vitamin D levels appear to affect bone healing and prolong treatment, with worsening trends with diabetes and obesity comorbidities.

Seasonal variation and sunlight exposure can impact serum vitamin D levels, potentially influencing lupus symptoms. We investigated seasonal vitamin D levels and their correlation with clinical manifestations and disease activity in systemic lupus erythematosus (SLE).

Serum 25(OH) vitamin D3 (25(OH)D3) levels were categorised as deficient (25(OH)D3 < 10 ng/mL), insufficient (10-30 ng/mL) and sufficiency (>30 ng/mL) in participants analysed in winter (n = 407) and summer (n = 377). Logistic regression analysis was performed to assess the impact of vitamin D levels on achieving a lupus low disease activity state (LLDAS), stratified by season.

The mean serum 25(OH)D3 levels differed significantly between the winter and summer measurement groups (22.4 vs. 24.2 ng/mL; p = .018). The prevalences of vitamin D deficiency, insufficiency and sufficiency in the winter group were 12.8%, 66.6% and 20.6%, respectively, compared with 4.5%, 67.9% and 27.6% in the summer group. Achieving LLDAS was highest in the vitamin D sufficiency group (winter: 56.6%, summer: 55%) and lowest in the vitamin D deficiency group (winter: 15.4%, summer: 13.6%), with significant differences (all p < .001). Multivariate analysis identified SLE disease activity index ≤4, normal anti-double-stranded DNA and vitamin D sufficiency as significant factors for achieving LLDAS in both seasons.

Sufficient vitamin D levels are important for achieving LLDAS in patients with SLE during winter and summer. Therefore, physicians should pay attention to the adequacy of vitamin D levels and consider recommending vitamin D supplementation for patients with vitamin D insufficiency.

Low intake of micronutrients is associated with health-related problems in nursing home residents. As their food intake is generally low, it is expected that their micronutrient intake will be low as well. The nutrient intake of 189 residents (mean age 85.0 years (SD: 7.4)) in five different Dutch nursing homes was measured based on 3-day direct observations of intake. Micronutrient intake, without supplementation, was calculated using the Dutch food composition table, and SPADE software was used to model habitual intake. Intake was compared to the estimated average requirement (EAR) or adequate intake (AI) as described in the Dutch dietary reference values. A low intake was defined as >10% not meeting the EAR or when the P50 (median) intake was below the AI. Vitamin A, thiamin, riboflavin, niacin, B6, folate, B12, C, D, E, copper, iron, zinc, calcium, iodine, magnesium, phosphorus, potassium, and selenium were investigated. Our data showed that vitamin and mineral intake was low for most assessed nutrients. An AI was only seen for vitamin B12 (men only), iodine (men only), and phosphorus. A total of 50% of the population had an intake below the EAR for riboflavin, vit B6, folate, and vitamin D. For reference values expressed in AI, P50 intake of vitamin E, calcium, iodine, magnesium, potassium, and selenium was below the AI. To conclude: micronutrient intake in nursing home residents is far too low in most of the nursing home population. A "food-first" approach could increase dietary intake, but supplements could be considered if the "food-first" approach is not successful.

Vitamin D plays a crucial role in calcium and phosphate metabolism, relating to bone health and preventing metabolic bone disorders such as rickets and osteomalacia. Vitamin D deficiency (serum 25-OH-D values <20 ng/mL or 50 nmol/L) is common also in Italian people; it is recommended to maintain levels above 30 ng/mL (75 nmol/L) in categories at risk. Supplementation and/or fortification with either ergocalciferol (vitamin D2) or cholecalciferol (vitamin D3) aimed to modify this condition have commonly been proposed. Studies about vitamin D intake are numerous in the literature but not adequately designed and are very often incomplete in Mediterranean Countries such as in the Italian population. On these bases, we performed a survey to validate a frequency food questionnaire (FFQ) specifically created to rapidly assess dietary vitamin D intake in Italian people. For this aim, the data of questionnaires were compared with results derived in the same population from a designed 14-day frequency food diary (FFD). Overall, a good correlation between FFQ and FFD was observed (r = 0.89, p < 0.001), both demonstrating a remarkably low vitamin D intake, irrespective of age and gender. Our data confirm that the vitamin D intake is very low in Italy, which likely contributes to hypovitaminosis D.

Sunlight contains ultraviolet B (UVB) radiation that triggers the production of vitamin D by skin. Vitamin D has widespread effects on brain function in both developing and adult brains. However, many people live at latitudes (about > 40 N or S) that do not receive enough UVB in winter to produce vitamin D. This exploratory study investigated the association between the age of onset of bipolar I disorder and the threshold for UVB sufficient for vitamin D production in a large global sample.

Data for 6972 patients with bipolar I disorder were obtained at 75 collection sites in 41 countries in both hemispheres. The best model to assess the relation between the threshold for UVB sufficient for vitamin D production and age of onset included 1 or more months below the threshold, family history of mood disorders, and birth cohort. All coefficients estimated at P ≤ 0.001.

The 6972 patients had an onset in 582 locations in 70 countries, with a mean age of onset of 25.6 years. Of the onset locations, 34.0% had at least 1 month below the threshold for UVB sufficient for vitamin D production. The age of onset at locations with 1 or more months of less than or equal to the threshold for UVB was 1.66 years younger.

UVB and vitamin D may have an important influence on the development of bipolar disorder. Study limitations included a lack of data on patient vitamin D levels, lifestyles, or supplement use. More study of the impacts of UVB and vitamin D in bipolar disorder is needed to evaluate this supposition.